GNU Guile: Growing article, with links to many related topics. [Wikipedia]
Guile: GNU's Ubiquitous Intelligent Language for Extension, a library implementation of the Scheme language plus various convenient facilities. Designed to be linked into programs to make them extensible.
Guile Object Oriented Programming System: GOOPS: Object-oriented extension to Guile; very close in spirit to Common Lisp Object System, CLOS (CLtL2), but adapted for Scheme language; gives full OO system with multiple inheritance, generic functions with multi-method dispatch.
guile-gtk: Guile bindings for Gtk+.
guile-gtk-general: Maillist for general discussions about the guile-gtk project.